Rapid response electrical switch and the like



June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8Sheets-Sheet 1 Inventors:

CZz'ffard A .fladye June 14, 1966- c. A. BODGE ETAL 8 Sheets-Sheet 2Filed May 15.

mull] [[Ill 3' Thom as Elivarza,

fnven tons CZzfford A. Bod

June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8Sheets-Sheet 3 vww Q Nmw m. QN

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Int/enters Clifford A. 5 0d RAPID RESPONSE ELECTRICAL SWITCH AND THELIKE Filed May 15 1961 8 Sheets-Sheet 4 mmm mk \1 I I 190 /94 Me asfnverz tons: Clifford A. ,Bodye, i Thomas .Eflvans, ua 7 June 14, 1966c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE Filed May 15 1961 8Sheets-Sheet 5 2/4 a 2 0 f) n 20a 200 /42 //02 2/6 m2 M6 m6 as asInventors: UZzff0rdA.B0d e, T amas .Eva zs,

June 14, 1966 c. A. BODGE ETAL 3,256,405

RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKE 8 Sheets-Sheet 6 Filed May15 1.961

[727/672 tors as 84 Cizffard A,,Bodye,

Thomas L. Evans,

June 14, 1966 c. A. BODGE ETAL RAPID RESPONSE ELECTRICAL SWITCH AND THELIKE Filed May 15 1961 8 Sheets-Sheet 8 F1916.

In ven tors. CZ ifford A ,Bad

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United States Patent RAPID RESPONSE ELECTRICAL SWITCH AND THE LIKECliiford A. Badge, Attleboro, and Thomas E. Evans,

Rehoboth, Mass, assignors to Texas Instruments Incorporated, Dallas,Tex., a corporation of Delaware Filed May 15, 1961, Ser. No. 109,933 4Claims. (Cl. 200-113) The instant invention relates to improvedelectrical circuit breakers and/or electrical switches having automaticoverload current protection. The instant invention is particularlyconcerned with circuit breakers which are practical for use inlow-current applications or in applications where relatively rapidoverload response is required.

It has been found that in general, where bimetallic tripping members areemployed, many problems have been encountered in providing a circuitbreaker which will effectively operate at a low current rating andprovide desirous response and protection. The instant invention employsa current-carrying wire-type thermal latch or tripping mechanism which,upon a predetermined overload of current or temperature, is adapted toelongate and actuate or trip the electrical circuit breaker or switch toprovide desired response. In operation of electrical switches which areactuated or controlled by a currentcarrying wire tripping mechanism suchas, for example, that shown in US. Patent No. 2,943,172, there is manytimes a time lag or finite time interval between the time that thecurrent-carrying wire mechanism trips the device, and the time that theprimary contacts of the electrical switch are separated to open thecircuit. During this time lag or interval, overload current is or maystill be flowing through the circuit and also through thecurrent-carrying tripping wire. Such current-carrying wires generallyhave a relatively small cross section and high resistance, and whensubjected to such overload currents during the aforementioned time lagor interval, dangers of burnout and deleterious shifts in calibrationbecome critical problems.

It is therefore one object of this invention to provide an electricalswitch of the class described, which employs a current-conducting Wireas part of a current overload tripping mechanism and which switchincludes means for protecting the current-conducting wire fromdeleterious overheating and/ or burnout which might result underexcessive current conditions.

It is another object or this invention to provide an electrical switchof the class described, which employs a current-conducting wire as partof a current overload tripping mechanism and which switch includesrelatively simple and economically constructed means for protecting thecurrent-conducting wire from deleterious overheating and/or burnoutwhich might result under excessive current conditions.

It is another object of the instant invention to provide a new andimproved manually operable circuit breaker having automatic overloadcurrent protection, and which is adapted to operate at relatively lowcurrent values, for example, currents less than five ampcres.

It is another object of the instant invention to provide an electricalswitch of the class described, the operation of which is relativelyunaffected by ambient temperature conditions or variations.

It is a further object of the instant invention to provide a new andimproved latching and tripping mechanism for electrical switches of theclass described.

Among the further objects of the instant invention may be noted theprovision of an electrical switch which is relatively compact, durable,accurate, reliable in operation; which is versatile and susceptible tovarying electrical ratings, including low current ratings; which willpro- Patented June 14, 1966 ice vide an accurate and fast response topredetermine overload current and temperature conditions; and which iseconomical to assemble and manufacture.

'Other objects will be in part apparent and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings, in which some of the various possibleembodiments of the invention is illustrated:

FIG. 1 is a top plan view of an electrical switch according tothe'instan't invention;

FIG. 2 is an enlarged sectional view of the switch shown in FIG. 1 takenalong line 2-2 of FIG. 1, showing the parts in a contacts-closedposition;

FIG. 3 is a view similar to FIG. 2, showing the parts in a contacts-openposition, with certain parts thereof in phantom;

FIG. 4 is a sectional view taken on line 44 of FIG. 2;

FIGS. 5 and 6 are isometric views respectively of a latch engageablemember and an adjusting screw member of the switch shown in FIGS. 1-4.

FIG. 7 -is a sectional view, with certain of the parts shown in phantomfor clarity of illustration, taken on line 77 of FIG. 2;

FIG. 8 is an enlarged sectional view taken on line 8-8 of FIG. 7,showing relative and operational movement between the parts;

FIG. 9 is a sectional view taken on line 99 of FIG. 8;

FIG. 10 is a sectional view taken on line 10-10 of FIG. 8;

FIG. 11 is a sectional view taken on line 1111 of FIG. 8;

FIG. 12 is an isometric view of a bell crank latching lever member ofthe switch shown in FIGS. 1-4;

FIG. 13 is an isometric view of a pair of current-carrying wiretrippings members of the latching structure of the switch shown in FIGS.1-4;

FIG. 14 is an isometric view of a rocker member forming a part of thelatching structure of the switch shown in FIGS. 1-4;

FIG. 15 is a view similar to FIG. 2 of the switch, according to anotherembodiment of this invention;

FIGS. 16 and 17 are views taken respectively on lines 1616 and 1717 ofFIG. 15;

FIG. 18 is a view taken on line 1 81 8 of FIG. 17; and

FIG. 19 is a plan view of the member shown in FIG. 18.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Dimensions of certain of the parts as shown in the drawings have beenmodified for the purposes of clarity of illustration.

It will be recognized that certain parts in several of the figures ofthe drawings, have been omitted for the purpose of clarity ofillustration.

The embodiment shown in FIGS. 1-14, as particularly described herein,takes the form of an electrical switch or circuit breaker indicatedgenerally by the numeral 20. Circuit breaker 20 includes a casing 22formed of an electrically insulating material, such as one of thecustomary molded plastics, and having its upper end open (as viewed inFIG. 2). Casing 22 is formed in two parts, which may be fastenedtogether, for example, by means of screws or rivets, as shown in FIG. 2.The open end of casing 22 is closed by a cover member which may besecured thereto, as by means of screws 26 (as-shown). An insulatingpiece 96 is disposed between cover member 24 and the open end of casing22.. Insulating piece 96 is tightly secured between cover member 24 andthe open end of easing by screws 26 (see FIG. 2). Switch includes afixed or stationary contact 28 mounted on exteriorly extending terminal27, a movable Contact 30, and means carrying the movable contact forpivotal movement about a common axis.

The means which mount the movable contact 30 for movement toward andaway from fixed contact 28, the manually operable actuating andresetting means, and the spring members which bias these parts of theswitch, are similar to that shown in the circuit breaker construction inU.S. Patent No. 2;813,16 8, issued November 12, 1957 to Mascioli et al.,and assigned. to the assignee of the instant invention, and are similaralso to that shown in US. Patent No.-2,613,296, granted on October 7,195 2, to M. 13. Wood. Reference may be had to these patents forspecific details of construction and of the cooperative relat-iOnshipbetween parts, such as the latching and actuating members, thecontact-carrying members, and manually operable resetting and actuatingmeans, which are shown to the left of line 77 in FIG. 2.

Switch 20 provides a new and improved current overload and trippingmechanism, referred to generally by numeral 100, and shown to the rightof line 77 of FIG. 2, which is particularly useful for (though notnecessarily limited to) switches of the type shown in the Mascioli etal. and Wood patents, supra.

The means mounting movable contact 30 for pivotal movement includes acontact-carrying arm on member 32 mounted on pivot pin 34. Pivot pin 34is supported at its ends in a pair of opposed recesses or socketsprovided on the interior of a pair of opposed internal walls- 23' and2-5 of casing 22. Also mounted on pivot pin 34 is a member 36. Member36. includes a loop 38 deformed therefrom to provide spaced portions 40,on each of which is mounted one end of a respective one of a pair ofsprings 42. The other ends of each of springs 42 are secured 22, as bestseen in FIG. 4. As will be clear from the description to follow, bellcrank lever 68 is pivotable to the right, as seen in FIG. 2, in acounterclockwise direction about its pivotal axis to move latchingmember or abutment 66 out of engagement with latch abutment 64 carriedby latch engageable member 62. Until latch bar 66 is moved out ofengagement with abutment portion 64 (by means to be described in greaterdetail below) the parts are in a position to releasably retain themovable contact in electrically conductive engagement with the matingfixed contact 28 in a manner pointed out as follows.

, As shown in FIGS. 2-4, latch engageable member 62 provides a camsurface 76 for co-operation with a roller 78. Member 36 provides a camsurface 80 for cooperation with rollers 82, 82 (as best seen in FIG. 4).Rollers 78, 82 and 82 (see FIG. 4) are respectively mounted in coaxialrelationship for rotation about a pin 84, which has its ends fixed inmutually spaced members 86, 86. Members 86, 86 and pin 84 together forma yoke pivotally mounted for movement about pin 88. A link 89 has itsopposite ends secured to members 86, 86 to aid and rigidify this yoke.Pin 88 passes in loosely interfitting engagement Within apertures ineach of members 86, 86 and insimilar interfitting engagement with anextension 90 of a push button 92. Push button 92 is confined within ahub 93 secured to cover member 24, for substantially rectilinearmovement toward and away from the interior of casing 22. Hub 93 issuitably secured in fixed relation to cover member 24 about an aperturein the latter through which button 92 extends. The opposite ends of pin88 ride in opposed longitudinal recesses 94, 94 provided by Opposedsidewalls 23 and 25 of casing 22, each of which extends to the open endof casto a transversely extending pin 46. Pin 46, like pin 34,

her 36 is resiliently biased away from contact-carrying arm 32 withwhich it co-operates, by means of a spring 48. Member 50 is mounted onmember 32 by means of a rivet 52, which rivet includes a projection54'which serves as a spring seat for spring 48. Member 36 provides aprojection 56 which serves as a spring seat for the other end of spring48. Member 50 provides a shoulder 58 which co-operates with an opposedshoulder 60 provided by member 36 to limit the extent to which members36 and 32 are biased away from each other by spring 48. It will beunderstood that so long as no restraining force is applied to eithermembers 32 or 36, they will pivot in unison about their common axis 34.Since members 32 and 36 are adapted to pivot in unison about theirrespective common axis 34, when in the absence of a restraint applied toeither of the members, springs 42 resiliently bias both members 32 and36 for movement in a direction to separate contacts 30 and 28.

Switch 20 includes a latch engageable member generally referred to bynumeral 62, and best shown in FIG. 5. Member 62 is mounted for pivotalmovement about pivot pin 34, and is biased for counterclockwise rotationthereabout (as seen in FIG. 2) by means of a tension spring 72, to bringa projection or abutment 64 fixedly carried thereby into engagement withan opposed projection or abutment 66 fixedly carried by a pivotallymounted bell crank lever 68- which forms part of the latching mechanismto be described in greater detail below.

As best shown in FIG. 5, latch engageable member 62 provides an apertureor eye 70 for attachment of one end of tension spring 72, the other endof spring 72 being Supported by pin 74. Pin 74 is mounted in a pair ofopposed recesses formed in walls 23 and 25 of casing ing 22, as bestseen in FIGS. 2 and 4. Button 92 also includes a transversely extendingpin 95, the opposite ends of which also ride in opposed recesses 94, 94.

Latching mechanism 100 Latching mechanism or assembly 100 includes aframe member 102, having a pair of sidewalls 104 and 106, as best seenin FIGS. 7 and 9. Frame member 102 further includes a transverselyextending wall 108 which connects and maybe integrally formed withsidewalls 104 and 106. Wall 108 includes an extension 110 which iselectrically connected and secured to an exteriorly extending electricalterminal 112, disposed and received within a recess 114 formed in casing22. Portion 110 may be secured to terminal 112, as by welding, to firmlysecure the parts together. Latching subassembly advantageou'sly can bemass produced as a separate subassembly unit and can be mounted as aunit within casing 22 by 'slidably inserting terminal 112 within a slot114 provided by each half of the casing 22. Latching unit 100 furtherincludes latching member 68 (best shown in FIG.- 12) which mounts latchabutment 66, as by means of rivets 67, as shown. Member 68 takes theform of a bell crank lever having a long leg 116 and a pair ofrelatively short legs 118 and 120 which may be formed integrally withleg 116. Legs 118 and 120 co-operate with leg 116 to provide a pair ofopposed spaced notches 122 and 124. Disposed within notches 122 and 124is a pin 126, as best seen in FIGS. 8 and 12. Pin 126 is fixed orsecuredto bell crank member 68, as by welding. The free ends of pin 126are disposed for rotation (in concert with bell crank 68) in sleeve orbearing members 128 and 130 which are mounted in sidewalls 104 and 106of frame 102, as shown. Bearing or trunnion members 128 and 130 areformed of an electrically insulating material, such as, for example, aceramic, and

are received within suitable apertures provided by sidewalls 104 and 106of frame 102. Bell crank lever 68 is thus adapted to pivot with pin 126in bearing members 128 and 130 to move abutment member 66 into and outof position for engagement by projection or abutment 64 of latchengageable member 62. Bell crank lever 68 is electrically connected withelectrical contact 30 by means of a pigtail 132, which electricallyconnects leg 116 and contact-carrying member 32. Contact-carrying member32 provides a struck-out projection 134 formed integrally therewith, towhich one end of pigtail 132 is electrically connected, as clearlyshown. Bell crank lever 68 is urged for pivotal movement in acounterclockwise direction (as seen in FIG. 8) by spring 136, as bestseen in FIGS. 2, 3 and 8. Spring 136 is received within, and one endthereof is seated in, an aperture 138 provided by casing 22. The otherend of spring 136 is disposed about a spring seat projection 140,provided by leg 116 of bell crank lever 68, as best seen in FIG. 7.

Latching mechanism 100 further includes a pair of electricallyconductive wires, which may be referred to as hot wires, 142 and 144, asbest seen in FIGS. 8 and 13. Hot-wire elements 142 and 144 are formed ofmaterials having a relatively high electrical resistance. By way ofexample, the materials forming hot wires 142 and 144 can be anickel-chrome alloy, such as that sold under the trademark Nichrome,"which is an alloy con sisting essentially of 15 %16% chromium, 59%62%nickel, about 24% iron, and 0.1% carbon. It is preferred that hot wires142 and 144 be of substantially rectangular cross section, asillustrated, but it is to be understood that they may take other forms(e.g., circular, elliptical or other polygonal cross-sectional shapes)within the practice of the instant invention. Each of hot wires 142 and144 are respectively provided with a layer of-electrical insulation 146,147, disposed thereabout throughout substantially the entire length ofthe hot wires, as best seen in FIG. 13. Hot wires 142 and 144 areelectrically connected together by means of a pigtail 148, as best seenin FIGS. 8 and 13. Ends 150 and 152 respectively of hot wires 142 and144 are mounted on a rocker arm generally referred to by numeral 154,which is best shown in FIG. 14. Rocker arm 154 includes a pair ofspaced, substantially parallel leg portions 156 and 158, which areinterconnected and may be formed integrally with portion 160. Rocker arm154, may be formed, for example, by stamping. Each of legs 156 and 158is respectively provided with a pair of opposed spaced and registeringnotches 162, 164 and 166, 168. vLegs 156 and 158 are respectivelyprovided with opposed and aligned registering apertures 170 and 172,which are disposed respectively intermediate notches 162, 164 and 166,168, as shown. Rocker member 154 is mounted on frame 102 for pivotalmovement about pin 174. The free ends of pin 174 are disposed withinsleeves 176 and 178 which are in turn respectively mounted and receivedwithin suitably formed apertures provided in sidewalls 104 and 106 offrame member 102, as best seen in- FIGS.

.8-10. Trunnion or bearing members 176 and 178 are or may besubstantially identical to members 128 and 130 described above. Each ofsleeve members 128, 130 and 176, 178 serve a dual function of providinga bearing for their respective pins and also serve as spacers tomaintain their respective parts in predetermined spaced assembledrelation. Ends 150 and 152 of hot wires 142 and 144 are advantageouslypivotally mounted on rocker arm 154, as will be described in greaterdetail below. Ends 150 and 152 are each respectively provided with aconnector plate or bracket 180, 182, which bracket members aresubstantially identical. Connector plates or brackets 180 and 182 arerespectively electrically connected and secured to ends 150 and 152,respectively of hot wires 142 and 144, as by riveting, or preferably, asby welding, as at 181 and 151, respectively. Brackets 180 includes apair of transversely extending fingers or projections 184, 186 andmember 182 includes a pair of similar fingers 188, 190. Fingers orprojections 184, 186 and 188, 190 respectively extend transversely andsubstantially perpendicular to the longitudinal axes of hot wires 142,144. Fingers 184, 186 and 188, 190 are respectively receivable withinopposed, aligned pairs of notches 162, 168 and 164, 166 to pivotallysecure ends and 152, respectively of hot wires 142 and 144 to the rockerarm 154. Each of fingers 184, 186; 188, 190 is provided with a roundedupper surface 192, which is received adjacent the apex of each ofnotches 162, 168; 164, 166 of rocker arm 154 to facilitate pivotalmovement therein and provide advantages to be described below. It is tobe noted that hot wire 142 is somewhat longer than hot wire 144. Each ofmembers and 182 respectively provide a bent-over lip portion 194 and 196to which end of pigtail 148 are electrically connected, as by welding.

The upper ends 198 and 246 respectively of hot wires 144 and 142 areeach respectively provided with a connecting bracket or plate 200, 248which are identical to each other, and similar to plates 180 and 182, asbest seen in FIG. 13. Connector plates or brackets 200 and 248 arerespectively electrically connected and secured to hot wires 144 and142, as by riveting or welding respectively, as at 218 and 254. Each ofconnecting plates or brackets 200 and 248, respectively, include a pairof projecting fingers 202, 204 and 250, 252 which extend transverselyand substantially perpendicular too the longitudinal axes of hot wires144 and 142. Each of fingers 202 and 204 are adapted to be receivedwithin a pair of spaced, opposed and aligned notches 206 and 208respectively provided by arms 118 and 120 of bell crank lever 68 (asbest seen in FIGS. 9 and 12). The lower edge surfaces of fingers 202 and204 are rounded, as at 210, to facilitate pivoting of fingers 202 and204 within their respective'notches 206 and 208 in a manner similar tothat described above for rounded portion 192 of fingers 184, 186;188,190.

Each of connector brackets 200 and 248 further include bent-overportions 212 and 249 to which pigtails 214 and 251 are respectivelyelectrically connected, as by welding. The other end of pigtail 214 iselectrically connected to leg 116 of ball crank lever 68, as at 216, asbest seen in FIGS. 7 and 8.

Sidewalls 104 and 106 of frame 102 respectively provide a pair ofopposed, spaced notches 222 and 224 which co-operate with wall108 toform a pair of opposed, aligned registering open-ended slots. Latchingassembly 100 further includes a thermally responsive plate generallyreferred to by numeral 226. Thermally responsive mounting plate 226 maybe formed of a conventional thermostatic multilayered material, forexample, a bimetallic material having a high expansion component 228 anda low expansion component 230, as shown, the high and low expansioncomponents being respectively indicated in the drawings by HES and LES.

As best seen in FIGS. 2 and 4, bimetallic mounting plate 226 is mountedand fixedly secured, as by welding, to a transversely extending pin 232,the ends of which project beyond the ends of bimetallic member 226.Bimetallic member 226 is thus adapted to rotate in concert or in unisonwith pin 232. The free ends of pin 232 are respectivelly received withinopen-ended slots 222 and 224 provided by frame 102, as described above,to pivotally mount bimetallic mounting plate 226 with respect to frame102.

Referring now to FIG. 4, bimetallic mounting member 226 is provided witha keyhole shaped slot 240 which comprises a narrow slotted section 242adjacent one end thereof, and a relatively wide slotted section 244adjacent the other end thereof. Connecting plate 248 pivotally mountsend 246 of hot wire 142 on bimetal mounting plate 226. Connecting plate248 may be pivotally secured to bimetal mounting plate 226 simply byinserting connecting bracket 248 through keyhole shaped slot 240, withfingers 250 and 252 disposed lengthwise of the slot, and then rotatingthe bracket 248 about its narrower shank portion 256, the width of whichis slightly less than the width of the wide keyhole portion section 244of the keyhole slot 240. After insertion and rotation of bracket member248, the bracket fingers 250 and 252 are disposed in engagement with theupper surface of bimetal mounting member 226 adjacent the edges of thewide slot portion 244, as best seen in FIG. 4. Each of fingers 250 and252 are provided with rounded, lower surface portions 258 (as best seenin FIG. 12) to facilitate pivotal movement thereof about the adjacentupper surface portion of bimetal member 226.

Referring now to FIG. 8, it can be seen that rotation of hell cranklever 68 in a counterclockwise direction (to disengage abutting latchportion 66 from abutting finger 64 of latch engageable member 62) underthe biasing force of spring 136 is normally resisted by hot wires 142and 144. End 198 of hot wire 144, which is pivotally connected to arms118 and 120 of the bell crank to the right of the pivotal axis throughpin 126 (as seen in FIG. 8) tends to resist counterclockwise rotation ofmember 68. Rotation of the rocker arm 154 is normally prevented by meansof its pivotal connection to each of hot wires 142 and 144, and by meansof the pivotal connection of end 246 of hot wire 142 to mounting plate226. The tension in hot wires 142 and 144 is so calibrated or adjusted(by means to be described below) that the hot wires normally tend toresist rotation of leg 116 of bell crank 68, and tend to retain leg 116and abutment 66 carried thereby, in a position for engagement byabutment 64 of latch engageable member 62, to permit movement of contact30 into engagement with fixed contact 28, and to releasably maintain thesame in a contactsclosed position.

Sidewalls .104 and 106 of frame 102 each respectively include aprojecting or extending wall portion 270 and 272, as best seen in FIGS.4, 7 and 8. Pigtail 251 is electrically connected to projecting wallportion 272 as by welding at 271, as best seen in FIGS. 7 and 8, toelectrically connect hot wire 142 to frame 102. Opposed projecting walls270 and 272 respectively provide a pair of opposed, spaced, aligned andregistering open-ended slots 274 and 276. Each of aligned, open-endedslots or notches 274 and 276 receive a respective one of a pair ofprojections 280 and 282 provided by a plate 284. Projections 280 and 282interfit with and are seated respectively in slots 274 and 276 to seatand mount plate 284, as best seen in FIG. 7. Plate 284 is provided witha bore or aperture 286 in which is disposed a calibrating or adjustingscrew member 290 having a threaded portion 292. As best seen in FIG. 6,calibrating member 290 includes a headed portion 294. Headed portion 294includes a narrow width portion 296 having a width which is slightlyless than that of the narrow slot portion 242 of keyhole shaped slot248. Adjusting screw 290 is secured to mounting and calibration plate226 by first inserting the head 294 of the screw into the wide portion244 of keyhole shaped slot 240, and then sliding the narrow widthportion 296 into the narrow slot portion 242. Narrow width portion 296co-operates with the sidewalls of narrow slot portion 242 to inhibit orlimit relative rotation between the adjusting screw and the bimetallicplate. The free threaded end of screw 290 is threadedly engaged with anut 298, which. thereby maintains headed-over flange portion 294 inengagement with the underside of the mounting and calibrating plate 226(as best seen in FIGS. 7 and 8).

Hot wires 142 and 144 are adapted to elongate, upon an increase intemperature thereof, which could be caused, for example, by an overloadcurrent flowing therethrough. Hot wires 142 and 144, when so elongatedby a predetermined amount, will permit leg 116 of bell crank lever 68 torotate in a counterclockwise direction under the bias of spring 136 andmove to the dashed-line position, as shown in FIG. 8, to disengageabutment latch member 66 from finger 64 to permit release and opening ofcontacts 30 and 28, in a manner to be described more fully below.Bimetallic mounting member 226 advantageously provides a simple andeconomical means for ambient compensation. Bimetal plate 226 is adaptedto flex upwardly to the dashed-line position, as shown in FIG. 8, uponan increase in ambient temperature, to move end 246 of hot wire 142upwardly. Movement of end 246 upwardly, as seen in FIG. 8, results intensioning hot wire 142, pivoting rocker arm 154 in a counterclockwisedirection, which in turn further tensions hot wire 144 to compensate forany elongation which may have taken place due to an increase in ambienttemperature, which thus avoids undesirable and deleterious calibrationshifts or nuisance tripouts. The bimetal mounting plate 226 is thuseffective to maintain the tension in the hot wires 142 and 144substantially constant irrespective of the ambient temperature, andthereby avoids undesirable and deleterious calibration shifts andinadvertent and nuisance tripouts of the switch which might otherwiseoccur on an increase of the ambient temperature in absence of thermallyresponsive mounting plate 226.

Bimetallic mounting plate 226, in addition to rendering the operation ofswitch 20 relatively insensitive to ambient temperatures, also servesthe function of a calibrating means for the switch. Calibration of theswitch 20 may be efiFected by suitable rotation of nut 298 aboutthreaded shank portion 292. It will be clear that, upon appropriaterotation of nut member 298 about threaded shank portion 292 (as bestseen in FIG. 8) that bimetallic member 226 will pivot either in aclockwise direction to increase tension on the hot wires 142 and 144, orbimetallic plate 226 will pivot in a counterclockwise direction (aidedby the spring force exerted by spring 136) to reduce the tension on hotwires 142 and 144. It will be clear that varying the tension in the hotwires 142 and 144 will be effective to vary the the operatingcharacteristics of the latching mechanism, and consequently, the

operating characteristics of the switch.

Latching assembly .100 further includes a layer of insulation 300disposed against the interior side of lower wall portion 110 of wall 108intermediate wall 110, and the pigtail 148, as best seen in FIG. '8.Another layer of electrical insulation 302 is provided intermediatepigtail 214 and bimetallic calibration and ambient compensating mountingplate 226, as best seen in FIG. 8.

The operation of circuit breaker 20 thus far described, is as follows:with the parts in the contacts-open position shown in FIG. 3, arm 36 isresiliently biased away from contact-carrying member 32 to the extentpermitted by the engagement of the respective shoulders 58 and 60 ofthese members. Also, member 36 and contact-carrying member 32 are biasedupwardly (as seen in FIG. 3) for rotation about pivot 34 in a clockwisedirection under the influence of springs 42, and latch engageable member62 is resiliently biased upwardly, as viewed in FIG. 3, for movement ina counterclockwise direction about pivot 34, under the influence ofspring 72.

It will be noted that with the parts in the position of FIG. 3, theforce exerted by spring 48 is greater than the force exerted by springs42, and that the combined force exerted by springs 42 is greater thanthe force exerted by spring 72. The result is that, upon depression ofpush button 92, rollers 82 ride along cam surface provided by member 36,whereby roller 78 moves against cam surface 76 provided by latchengageable member 62, thereby to swing the latch engageable member 62 ina clockwise direction about the axis of pin 34 until projection 64 movesinto engagement with abutment 66 provided by bell crank latch member 68.Thereafter, roller 78 moves along cam surface 76 thereby to move rollers82, 82 against cam surface 80- and corner 81 provided by member 36,causing member 36, along with member 32, to pivot in a counterclockwisedirection about the axis of pin 34. Members 36 and 32 pivot in unisonwith each other until movable contact 38 comes into engagement withfixed contact 28. At this point, lost motion of member 36 with separatedfrom each other.

cuiting conditions. "loads of comparatively high magnitudes, hot wires142 9 respect to member 32 ensues, whereby member 32 remains stationarywhile member 36 continues to move to the position shown in FIG. 2, atwhich the respective shoulders 58 and 60 provided respectively bymembers 32 and 36 are It will be noted .that with the parts in theposition shown in FIG. 2, wedging'means or rollers 78 and 82 have movedinto an overcenter position with respect to the latch engageable member62 and memto terminal 112.

It will be recognized that by wedging the parts into overcenterrelationship with the structure as described above, the circuit breakerinherently possesses high shock and vibration resistance.

1 The electrically conductive path between the terminals 27 and 112 willremain intact until the latched condition described above is disruptedin any one of several ways.

First, push button 92 may be manually and forciblyretracted from thewedging overcenter relationship shown .in FIG. 2, whereby the parts willquickly return under the influence of the respective springs to theposition shown in FIG. 3.

Alternatively, the parts are movable from the position shown in FIG. 2to that shown in FIG. 3, upon movement of the abutment 66 carried bybell crank latch lever 68 away from engagement with projection 64carried by latch engageable member 62. As noted above, leg 116 of bellcrank latch member 68 is movable to the right and pivotable about pin126 in a counterclockwise direction, as viewed in FIG. 3, upon theoccurrence of a predeterminedcurrent overload. Such current overloadwill heat hot wires 142 and 144, and the resultant elongation thereofwill permit arms 1118 and 120 of bell crank lever 68 and also leg 116 ofbell crank lever 68, to pivot in a counterclockwise direction about theaxis of pin 126 under the bias and influence of spring 136. Elongationof hot wires 142 and 144 and consequent tripping of the switch 20 willresult upon the occurrence of predetermined moderate current overload,and also with those of comparatively high magnitudes, such as might beoccasioned by short cir- Upon the occasion of current overand 144 willrapidly elongate and effect rapid and substantial movement of leg 116 ofbell crank lever 68 to Y quickly move abutment 66 out of engagement withabutment 64 of latch engageable member 62.

Upon such disengagement between abutments 64 and 66, latch engageablemember 62 will first pivot in a clockwise direction (as seen in FIG. 3)since the combined force exerted by springs 42 added to the forceexerted by spring 48 is of a much greater magnitude than that of theforce exerted by spring 72. In this manner, the parts i are unlatchedand member 36 moves upwardly, as viewed in FIG. 2, thereby moving roller78 against latch engageable member -62, causing the latter to pivot in aclockwise direction against the bias of spring 72. The combined effectof springs 42, 42 and spring 48 is to snap the shoulder 60 provided bymember 36 against the adjacent fixed contact with which it co-operates,may be more effectively broken. Continued movement of members 36 and 32brings the parts back to the contacts-open position shown in FIG. 3.Meanwhile, the initial counterclockwise movement of latch engageablemember 62 about the axis of pin 34 in combination with the effect ofspring 72 and roller 78, results in movement of this member wherebyslots 71 and 73 provided by member 62 ride along pin 34. Latchengageable member 62 and push button 92 then return to the positionshown in FIG. 3 under the influence of spring 72. From the above, itwill be noted that circuit breaker 20 is trip free of push button 92,and that upon the occurrence of a fault or current overload in thecircuit to which the circuit breaker is connected, contacts 28 and 30will be opened, even though push button 92 may be held in a depressedposition; and that so long as such a fault exists, depression of thepush button will be ineffective to close the contacts.

Shunting contact arrangement As pointed out above, current traversesboth of the hot wire elements in circuit breaker 20. Upon the occurrenceof current overloads of a comparatively large magnitude (for example, ofthe nature of many times the rated current) there is a danger that thehot wire elements 142 and 144 may suffer burnout or be otherwisepermanently damaged by these large currents during the relatively shorttime interval between disengagement of latch abutment member 66 andabutment 64, and the opening of contacts 30 and 28 to open the circuit.The instant invention advantageously provides a simple and inexpensivemeans to obviate this danger. Such means takes the form of a shuntingarrangement which includes a pair of shunting contacts 352 and 354, asbest seen in FIGS. 2 and 8. Shunting contact 352 is electricallyconnected to and carried by leg 116 of bell crank lever 68 for movementtherewith, as best seen in FIGS. 3, 8 and 12. Stationary shuntingcontact 354 is mounted on and electrically connected to frame '102, asbest seen in FIGS. 7 and 9. Leg 116 of bell crank 68 is provided with alayer of electrical insulation 360 adjacent fixed'shunting contact 352,as best seen in FIGS. 3 and 8.

Referring now to FIG. 8, the dashed-line position of the latchengageable member 62 illustrated therein corresponds to thecontacts-open position shown in FIG. 3. The position of latch engageablemember 62, as shown in solid lines in FIG. 7, wherein abutment 64 is inengagement with the latchabutment 66, corresponds to the contacts-closedposition shown in FIG. 2. Leg 116, in moving from the solid to thedashed line position shown in FIG. '8, upon the occurrence of apredetermined current overload, is effective not only to disengage thelatch abutment 66 and abutment '64 to effect opening of contacts 30 and28, but also is effective to quickly move shunting contact 352 from thesolid to the dashed line position to effect a closing of the shuntingcontacts 352 and 354 to immediately shunt the current out of the hotwire elements 142 and 144, and thereby advantageously avoiddanger ofburnout or permanent damage to the hot wires 142 and 144 which mightresult from such excessive current overloads. The protection afforded byshunting contacts 352 and 354 permits using relatively high resistancehot wires of relatively low thermal mass, which affords fast response oncurrent overloads.

When shunting contacts 352 and 354 are closed during the relativelyshort time interval after disengagement of latch abutment 66 andabutment 64, and prior to opening of contacts 30 and 28, current willflow in the following manner: through terminal 27, to fixed contact 28,to movable contact 30, to contact arm 32, through extension 134 ofcontact arm 32, through pigtail 132, to leg 116 of hell crank 68, tomovable shunting contact 352, to fixed shunting contact 354, to frame102, to wall portion 110 of frame 102, to terminal 112. contacts 352 and354 are operable only during the interval between disengagement of thelatch abutment 66 and abutment 64 and the opening of contacts 30 and 28to open or de-energize the circuit, which contacts 30 and 28 7 control.It should be understood that the short time interval, as referred toherein, includes the time required for contacts 30-and 28 to open afterabutments 64 and 66 It is to be noted that the shunting are disengaged,as well as the time required for dissipation of 'any arcing that maytake place after contacts 30 and 28 are opened. As hot wires 142 and 144cool and contract, contacts 352 and 354 will separate. It is also to benoted that leg 116 of bell crank lever 68 can disengage abutment 66 fromabutment 64 without moving far enough in a counterclockwise direction toclose shunting contacts 352 and 354, for example, with a slow rate ofrise condition. The shunting contacts advantageously operate only onhigh surges of current and not during slow rate of temperature riseconditions. Thus, the danger of inadvertently shorting the current outof the hot wire sensing elements, for example, upon an increase inambient temperature, is advantageously averted.

The pivotal connection between the ends of the hot wires and the rockerarm 154, legs 118 and 120 of bell crank lever 68, and mounting plate226, uniquely and advantageously avoids undesirable overstress ing andpossible calibration shifts and rupture which might otherwise resultwith other types of connections, e.g.,-a welded arrangement. Thus, uponelongation and rotation of parts, the ends of the hot wires pivot abouttheir respective connections and maintain substantially all of thestress in the hot wires in the form of tensile stress which is exertedaxially of the hot wires. This advantageously avoids creation of momentsand bending stresses of the hot wires about their respectiveconnections.

Ambient compensation may also be achieved by replacing the polymetallicthermostatic type mounting plate 226 with a monolayered mounting plate,and forming frame 102 and the monolayered mounting plate of a materialor materials having substantially the'same cefiicient of thermalexpansion as that of hot wires 142 and 144. Ambient compensation couldalso be achieved by making plate 280 of a thermostatic material, such asbimetal, in which case mounting plate 226 could be formed of monometalor a single layered material.

Embodiment of FIGS. 15-19 In FIGS. 15-19 is shown a second embodiment ofthis invention, in which like numerals designate parts like those shownin the FIG. 1 embodiment, further verbal description in which respect isunnecessary. The operation of circuit breaker 4001s substantiallysimilar to that described above for circuit breaker 20. The point ofdeparture in the FIG. 15 embodiment is in the latching mechanismassembly unit, which in this form of the invention, is generallyreferred to by numeral 401. Unit 401 includes a frame member 402, whichcomprises a pair of sidewalls 404 and 406 and a transversely extendingwall 408 which connects and may be integrally formed with sidewalls 404and 406. Wall 408 includes an extension 410 which is electricallyconnected and secured to exteriorly extending terminal 112. Frame 402also includes an upper wall portion 411 extending transversely of andpreferably formed integrally with wall 408, as shown. Latching unit 401further includes a latching member 468 in the form of a bell crank leverhaving a long leg 416 and a short leg 418. Leg 416 mounts abutmentmember 66, which abutment member 66 is identical to that of circuitbreaker 20, and serves the same function.

Latching mechanism 401 includes a single, continuous electricallyconductive hot wire doubled into a U-shape to form two legs or portions442 and 444. The bight portion between legs 442 and 444 of the hot wireis disposed about a rocker arm generally referred to by numeral 453,which is best seen in FIGS. 18 and 19. Rocker arm 453 includes a pair ofspaced, substantially parallel leg portions 456 and 458. Rocker arm 453is mounted on frame 402 for pivotal movement about pin 174,substantially in the manner described above for the pivotal mounting ofrocker member 154. As best seen in FIGS. 18 and 19, rocker arm 453provides a pair of spaced notches 455 and 457 which receive hot wirepor- .tions 442 and 444 therein ,to inhibit relative lateral movementbetween the hot wire and the rocker arm 453. Leg 418 provides anaperture 419 and an open-ended slot 421, as best seen in FIG. 16. Freeend 443 of leg portion 442 of the hot wire is disposed in slot 421 andis electrically connected and fixedly secured to leg 418, as by welding,as best seen in FIG. 16. Upper portion 411 provides an open-ended slot413, as best seen in FIGS. 15 and 16. The free end 445 of leg 444 of thehot wire extends through aperture 419 in leg 418, through the slot 413,and

is electrically connected and fixedly secured to the upper surface ofwall portion 411 of frame 402, as by welding, as best seen in FIGS. 16and 17. Leg 416 of bell crank 468 is electrically connected to extendingportion 134 of contact arm 32 by means of pigtail 132, in the mannerdescribed above for circuit breaker 20.

Bell crank member 468 is fixedly connected to a pin 126, as by welding,as best seen in FIGS. 15 and 17. The free ends of pin'126 are disposedfor rotation (in concert with bell crank 468) in sleeves or bearingmembers 128 and 130 which are mounted in sidewalls 404 and 406 of frame402, in the manner described above for circuit breaker 20. Bell cranklever 468 is thus adapted to pivot with pin 126 to move abutment member66 into and out of position for engagement by abutment member 64, in

the manner described above for circuit breaker 20. Spring 136 engagesprojection 140 on leg 416 to resiliently urge bell crank lever 468 forpivotal movement in a counterclockwise direction, as seen in FIG. 15.

Latching subassembly 100 further includes a calibration arrangementwherein upper wall section 411 of frame 402 serves as a calibratingmeans, in a manner somewhat similar to mounting plate 226 of circuitbreaker 20. Frame 402 includes a pair of projecting or extending wallportions 470 and 472 (similar to wall portions 270 and 272 of circuitbreaker 20) as best seen in FIG. 17. Opposed projecting wall portions470 and 472 respectively provide a pair of spaced, opposed, aligned andregistering open-ended slots 474 and 476, as best seen in FIGS. 16 and17. Each of aligned open-ended slots or notches 474 and 476 receive arespective one of a pair of projections 480 and 482 provided by a plate484. Plate 484 provides a bore or aperture 486 in which is disposed acalibrating or adjusting screw member 490 having a threaded portion 492.As best seen in FIG. 17, the calibrating member includes a headedportion 494 which is identical to headed portion 294 of calibratingmember 290, as best seen in FIG. 6. Headed portion 494 includes a narrowwidth just slightly less than that of the slot 413 in member 411,

which inhibits relative rotation between portion 411 and the adjustingscrew. Adjusting screw 490 is secured to the calibrating portion 411 byfirst inserting the head 494 of the screw into the slot portion 413, andthen disposing the threaded portion 492 into aperture 496 of plate 484.

The threaded end portion 492 is then threadedly engaged with a nut 498which maintains headed over flange portion 494 in engagement with theunderside of the calibrating portion 411, as best seen in FIG. 17.

Calibration of switch 400 may be effected by suitable rotation of nut498 about shank portion 492, in the manner described above for adjustingscrew 292 of switch 20. It will be clear that upon appropriate rotationof the nut 498 about the threaded portion 492, that portion 411 will bemoved upwardly, as seen in FIG. 15, pivoting about its bight orconnecting bent portion with wall 408 of frame 402. It is to be notedthat when portion 411 is moved upwardly, its joint with wall 408 isdeformed and stressed, tending to resiliently urge portion 411 formovement downwardly, as seen in FIG. 15, which downward movement isresisted by engagement of portion 411 with headed-over portion 494 ofthe adjusting screw 490. Upward movement of portion 411, as seen in FIG.15, serves to increase the tension in the hot wire legs 442 and 444 tovary the operating characteristics of the latching mechanism andconsequently the operating characteristics of the switch 400.

Latching mechanism 401 further includes a shunting contact arrangementsimilar to that of circuit breaker 20 and includes a pair of shuntingcontacts 452 and 454 which may be identical to shunting contacts 352 and354 of switch 20. Stationary shunting contact 454 is mounted on andelectrically connected to frame member 402, as best seen in FIG. 17, andmovable shunting contact 452 is electrically connected to and mounted onbell crank 468 for movementtherewith, in the manner described above forshunting contact 354 and bell crank member 368 of switch 20.

Ambient compensation may be providedfor circuit breaker 400 by a numberof means. For example, ambient compensation may be achieved by formingplate member 484 of a thermostatic, polymetallic material, such as athermostatic bimetal. Ambient compensation can also be achieved byforming frame 402 of a material or materials having substantially thesame coefficient of thermal expansion as that of the hot wire element.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above methods without departingfrom the scope of the invention, it is intended that all mattercontained in the above description or shown in the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense, and it is also intended that the appended claims shall cover allsuch equivalent variations as come within the true spirit and scope ofthe invention.

We claim:

1. An electrical switch comprising a casing; first and second electricalterminals mounted in said casing and extending exteriorly thereof forconnection to an external circuit; a first electrical contactelectrically connected to said first terminal; a movable electricalcontact electrically connected with said second terminal and disposedwithin said casing for movement into and out of engagement with saidfirst contact; means resiliently urging said movable contact formovement in a contacts-opening direction; releasable latch means forholding said movable contact in engagement with said first contactagainst the urging of said resilient means, said releasable latch meansbeing engageable with a detent to maintain said contact in a latchedcontacts-closed position; an overload responsive tripping mechanism fordisengaging said latch means from said detent to permit said movablecontact to move to a contacts-open position under the bias of saidresilient means, said tripping mechanism comprising a frame member; saidframe member being electrically connected with said second terminal; abell crank lever pivoted to said frame member, said detent being carriedby one leg of said bell crank lever; spring means urging said bell cranklever for pivotal movement in a direction to move said detent out ofengagement with said latch means; first and second current-conductingwire portions electrically connected together; a composite thermostaticplate member mounted on said frame member; adjusting means operativelyconnected with said thermostatic plate member for calibrating saidswitch; one end of said first current-conducting wire portion beingconnected 'with said thermostatic plate member and the other end thereofbeing con nected to a first portion of a rocker arm; one end of saidsecond wire portion being connected to a second portion of said rockerarm and the other end thereof being connected to the other leg of saidbell crank lever; said rocker arm being pivotally mounted on said frameintermediate said first and second portions thereof, said first wireportion being electrically connected to one of said contacts and saidsecond wire portion being electrically connected to said frame member;said current-conducting wire portions being tensioned by said springmeans and normally retaining and positioning said lever and detent forengagement with said latch means; and said currentconducting wires beingoperative upon a predetermined increase in temperature thereof toelongate and permit said lever to move said detent out of engagementwith said latch means.

2. The electrical switch as set forth in claim 1 and wherein theconnections between the respective ends of said first and second wireportions to said thermostatic plate member, rocker arm and said otherleg of said bell crank lever are pivotal connections.

3. The electrical switch as set forth in claim 1 and wherein saidadjusting means comprises a rotatable threaded member having a portionengageable with said composite thermally responsive plate member formoving the latter relative to said frame member to vary the tension insaid current-conducting wire portions and thereby effect calibration ofsaid switch.

4. The electrical switch as set forth in claim 1 and wherein said frame,adjusting means and current-conducting wire portions are formed ofmaterial having substantially the same coefficient of thermal expansionthereby providing for ambient compensation.

References Cited by the Examiner UNITED STATES PATENTS 2,096,608 10/1937 Combi 200-1 16 2,320,117 5/1943 Ayers 200113 2,656,437 10/ 1953Allen 200116 2,689,239 9/1954 Bell 200122 2,943,172 6/ 1960 Ingwersen200116 3,021,404 2/1962 Wood 2001 16 3,046,371 7/1962 Jencks 200883,097,279 7/ 1963 Whinery 200122 3,134,873 5/1964 Malone et a1 2001163,142,737 7/ 1964 Brackett 200116 3,158,715 11/1964 Ingwersen 200116ROBERT MACON, Acting Primary Examiner. BENARD A. GILHEANY, Examiner.

A. M. LESNIAK, M. GINSBURG,

Assistant Examiners.

1. AN ELECTRICAL SWITCH COMPRISING A CASING; FIRST AND SECOND ELECTRICALTERMINALS MOUNTED IN SAID CASING AND EXTENDING EXTERIORLY THEREOF FORCONNECTION TO AN EXTERNAL CIRCUIT; A FIRST ELECTRICAL CONTACTELECTRICALLY CONNECTED TO SAID FIRST TERMINAL; A MOVABLE ELECTRICALCONTACT ELECTRICALLY CONNECTED WITH SAID SECOND TERMINAL AND DISPOSEDWITHIN SAID CASING FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH SAIDFIRST CONTACT; MEANS RESILIENTLY URGING SAID MOVABLE CONTACT FORMOVEMENT IN A CONTACTS-OPENING DIRECTION; RELEASABLE LATCH MEANS FORHOLDING SAID MOVABLE CONTACT IN ENGAGEMENT WITH SAID FIRST CONTACTAGAINST THE URGING OF SAID RESILIENT MEANS, SAID RELEASABLE LATCH MEANSBEING ENGAGEABLE WITH A DETENT TO MAINTAIN SAID CONTACT IN A LATCHEDCONTACTS-CLOSED POSITION; AN OVERLOAD RESPONSIVE TRIPPING MECHANISM FORDISENGAGING SAID LATCH MEANS FROM SAID DETENT TO PERMIT SAID MOVABLECONTACT TO MOVE TO A CONTACTS-OPEN POSITION UNDER THE BIAS OF SAIDRESILIENT MEANS, SAID TRIPPING MECHANISM COMPRISING A FRAME MEMBER; SAIDFRAME MEMBER BEING ELECTRICALLY CONNECTED WITH SAID SECOND TERMINAL; ABELL CRANK LEVER PIVOTED TO SAID FRAME MEMBER, SAID DETENT BEING CARRIEDBY ONE LEG OF SAID BELL CRANK LEVER; SPRING MEANS URGING SAID BELL CRANKLEVER FOR PIVOTAL MOVEMENT IN A DIRECTION TO MOVE SAID DETENT OUT OFENGAGEMENT WITH SAID LATCH MEANS; FIRST AND SECOND CURRENT-CONDUCTINGWIRE PORTIONS ELECTRICALLY CONNECTED TOGETHER; A COMPOSITE THERMOSTATICPLATE MEMBER